1. Technical Field
The technical field relates to a communication system and a communication method, and more specifically, relates to a communication system and a communication method for more reliable streaming in a communication system in a home network environment including a plurality of communication devices.
2. Description of Related Art
In recent years, FTTH (Fiber To The Home) has been popularized as means for connecting a personal computer at home to the Internet. At home, a home network has begun to be used, by which home appliances, computers, and other peripheral devices are interconnected for device-to-device communication. It is expected that in future, the home network is more and more popularized as a network for transmitting and receiving contents among devices connected over the network, and for providing convenient and comfortable user experiences.
For example, at home, it is possible to use, as a server device, an AV device having a video receiver unit such as a TV tuner and having a storage unit such as a hard disk, and to transmit a video content stored in the server device to a client device in another room through the home network. Thus, it is possible to stream and play back data; for example, the client device can receive a video content and simultaneously play back the video content.
A server device performing such streaming generates transmitting data through an encoding process, etc., and sends the transmitting data to the home network. On the other hand, a client device performing playback of streamed data temporarily stores received data in a buffer, and then, sequentially decodes and plays back the stored data.
However, a plurality of data communications may be in contention with each other over the home network. When such a plurality of data communications are in contention with each other, a shortage of a communication bandwidth occurs, thus causing problems such as a delay in streaming.
Various methods have been proposed for overcoming the contention of data communications. For example, Patent Document 1 discloses a configuration of a priority-based QoS (Quality of Service) technique for allocating a bandwidth to respective pieces of communication data according to priority. For example, in order to achieve real-time playback when streaming video data, it is necessary to transmit packets of the video data from a streaming server to a streaming client without delay. Meanwhile, some data packets allow a temporal delay. Therefore, a communication process is performed such that streaming data is set with a priority higher than that of normal communication data to differentiate between their priorities with which each data is processed.
When using the priorities, the contention of data communication is checked, for example, as follows. A certain length of check period is provided before starting delivery of new streaming data from a server device, and load data is transmitted with a priority lower than an original normal priority set for delivering the streaming data. The conditions for which the load data transmitted with the low priority being set are examined to determine whether or not to use the original normal priority for streaming transmission. If it is determined that the original normal priority can be used, then streaming data is transmitted with the original normal priority.
Even if another streaming transmission is simultaneously performed during the check period, it is possible to prevent that load data with a low priority affects existing streaming transmission with a high priority. That is, in the case in which the existing streaming is being performed, the load data never takes a bandwidth from the existing streaming, and accordingly, the load data does not distort a reproduced image at a client playing back the existing streaming.